The present invention relates to a microwave integrated circuit.
In conventional microwave integrated circuits which comprise a plurality of interconnected circuits of different functions, the operating characteristics of the individual circuits are not reflected faithfully in the overall operating characteristic of the integrated circuit due to the shielding effect of a casing in which the circuits are housed.
Specifically, in a microwave integrated circuit frequency converter which comprises an amplifier, mixer and local oscillator, the operating characteristics of the individual circuits can be fully exploited if the interconnecting parts of the converter are appropriately designed. However, the shielding effect of the casing adversely affects the various operating factors including input VSWR, noise figure, leakage of local oscillator output, image suppresion ratio and conversion gain. In a local oscillator having a dielectric resonator, the resonator tends to couple with a particular waveguide resonance mode of the shield case to such a degree that the oscillator ceases to generate an output.